Memories change over time. Looking back on some stuff I am a little bit horrified that I didn't do more to stop bullying.
In third or fourth year at school we had an English boy join us and he was bullied horribly. At PE, his clothes and bag would be put in the shower and soaked. I heard that someone shat in his shoe once. I got on fine with him but didn't speak up or confront anyone.
In fifth year, a few us us set up a safe space in the school (a cupboard). The school allowed us this, just a place where one or two prefects would sit and where any kid that was being bullied could spend their breaks or lunchtimes with us and not be in the playground. No idea if this helped anyone, but there were a few guys who regularly came and sat with us. One boy was really small and was best known for playing bagpipes. he looked terrified all the time.
Since school nothing comes to mind.